In a typical electric vehicle a single speed gearbox is used between the traction motor and the differential. The ability to use a single speed gearbox rather than the multi-speed gearbox required in a conventional vehicle is the result of the wide useful operating range, both in terms of power and torque, of an electric motor versus that of an internal combustion engine.
While a single speed gearbox may be used with an electric vehicle, its use is not without drawbacks. For example, because of the maximum speed limit of the motor and the requirement in a high performance car to reach a certain top speed, the gear ratio is typically chosen to be longer than what would be optimal to provide crisp initial acceleration from a standstill. Additionally, due to torque ripple and vibrations, motor torque may be limited at very low rotating speeds. As a result, initial acceleration from a standstill in a typical electric vehicle is typically more sluggish than what would be expected given the drivetrain's characteristics.
Accordingly, what is needed is a dual speed gearbox that may be optimized for the operating characteristics of an electric motor, thereby providing the desired level of performance throughout the vehicle's operating range. The present invention provides such a dual speed gearbox.